The Standing Rock Sioux Tribe praised President Obama for the decision, while an angry GOP lawmaker called president Obama and protesters ‘lawless.’

The U.S. Army Corps of Engineers announced on Sunday that it will not allow the proposed Dakota Access Pipeline to cross under Lake Oahe in North Dakota, CNN reports.

Jo-Ellen Darcy, assistant secretary of the Army (Civil Works), said the Army Corps would “explore alternate routes for the pipeline crossing.”

Native Americans and environmentalists celebrated the decision. The Standing Rock Sioux Tribe has opposed the pipeline because the proposed route was near their reservation. They feared that a spill would contaminate their water supply.

US Army will not allow North Dakota oil pipeline under a reservoir it controls, Sioux activists say https://t.co/e519hCkmDb

“We wholeheartedly support the decision of the administration and commend with the utmost gratitude the courage it took on the part of President Obama, the Army Corps, the Department of Justice and the Department of the Interior to take steps to correct the course of history and to do the right thing.”

Scores of veterans were the latest to join thousands of protesters who support the Standing Rock Sioux, many of the demonstrators living in makeshift shelters at the site.

The $3.7 billion proposed project called for a 1,172-mile pipeline to run through four states, transporting approximately 470,000 barrels of oil daily.

Not everyone is pleased with the decision. North Dakota GOP Rep. Kevin Cramer, unleashed harsh criticism of President Barack Obamaand the demonstrators in a statement:

“I hoped even a lawless president wouldn’t continue to ignore the rule of law. However, it was becoming increasingly clear he was punting this issue down the road. Today’s unfortunate decision sends a very chilling signal to others who want to build infrastructure in this country. Roads, bridges, transmission lines, pipelines, wind farms and water lines will be very difficult, if not impossible, to build when criminal behavior is rewarded this way.”

This environmentalists’ victory could be brief. The Los Angeles Times said President-elect Donald Trump recently restated his support for the pipeline project. Consequently, he could order a reversal of the Army Corps’ decision.